Based on what I recall from physics, even with a 5V 2.1A USB wall charger won't give you the full effect from a LR atty.
Ohm's law is I=V/R, where I is current in amperes, V is volts, and R is resistance in ohms.
So with 5V and 1.5Ω you get 3.33 amps, which is more than the charger can...